Multi-break compressed-gas circuit interrupter with separate storage volume for each break and single supply valve for associated supply volume



p 1965 R. E. FRIEDRICH ETAL 3,207,878

MULTIBREAK COMPRESSED-GAS CIRCUIT INTERRUPTER WITH SEPARATE STORAGEVOLUME FOR EACH BREAK AND SINGLE SUPPLY VALVE FOR ASSOCIATED SUPPLYVOLUME Filed May 31, 1961 4 Sheets-Sheet 1 0 1 0 q- IO .J

B N ID M m B m m .1

3 o EL WITNESSES INVENTORS Robert E. Friedrich 8 Joseph Sucho p 21, 1955R. E. FRlEDRlCH ETAL 3,207,373

MULTI-BREAK COMPRESSEDGAS CIRCUIT INTERRUPTER WITH SEPARATE STORAGEVOLUME FOR EACH BREAK AND SINGLE SUPPLY VALVE FOR ASSOCIATED SUPPLYVOLUME Filed May 51, 1961 4 Sheets-Sheet 2 p 1955 v R. E. FRIEDRICH ETAL3,2

MULTI-BHEAK COMPRESSED GAS CIRCUIT INTERRUPTER WITH SEPARATE STORAGEVOLUME FOR EACH BREAK AND SINGLE SUPPLY VALVE FOR ASSOCIATED SUPPLYVOLUME 4 Sheets-Sheet 5 Filed May 51, 1961 Sept. 21, 1965 R. E.FRIEDRICH ETAL 3,

MULTI-BREAK COMPRESSED-GAS CIRCUIT INTERRUPTER WITH SEPARATE STORAGEVOLUME FOR EACH BREAK AND SINGLE SUPPLY VALVE FOR ASSOCIATED SUPPLYVOLUME Filed May 51, 1961 4 Sheets-Sheet 4 U mu United States Patent3,207,878 MULTI-BREAK COMPRESSED-GAS CIRCUIT IN- TERRUPTER WITH SEPARATESTORAGE VOL- UME FOR EACH BREAK AND SINGLE SUPPLY VALVE FOR ASSOCIATEDSUPPLY VOLUME Robert E. Friedrich, Baldwin Born, and Joseph Sucha,

Port Vue, Pa., assiguors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Filed May 31, 1961, Ser.No. 113,701 6 Claims. (Cl. 200-148) This invention relates tocompressed-gas circuit interrupters, and, more particularly, toarc-extinguishing structures and operating mechanisms therefor.

A general object of the present invention is to provide an improvedcompressed-gas circuit interrupter in which a predetermined quantity ofcompressed gas is utilized during an opening operation of theinterrupter.

A more specific object of the present invention is to provide animproved compressed-gas circuit interrupter, particularly suitable for amulti-break construction, in which a plurality of compressed-gas circuitinterrupting units are employed in series, and a predetermined quantityof compressed gas is utilized for arc extinction at each unit.

In United States patent application filed January 23, 1959, Serial No.788,668, now United States Patent 3,057,983, issued October 9, 1962, toRussell N. Yeckley, Joseph Sucha and Benjamin P. Baker, and assigned tothe assignee of the instant application, there is disclosed and claimeda high-power compressed-gas circuit interrupter of the type employing aplurality of serially-related breaks. In the interrupting constructiondisclosed by the aforesaid application, a high-pressure reservoirchamber and a blastvalve mechanism are disposed adjacent one end of anarc-extinguishing assemblage, which bridges the interior ends of a pairof spaced terminal bushings within a grounded metallic tank structure.The general operation of the aforesaid interrupter is such that duringthe opening operation a single blast valve is opened to permit theblasting of gas from such high-pressure reservoir chamber down through aplurality of blast tubes and into the plurality of serially-relatedgas-blast interrupting units. The construction is such that the unitsmore remote from the high-pressure reservoir chamber are supplied withcompressed gas at the same time as the more immediately disposed units,but all of the gas-blast units derive their blast pressure from a singlereservoir tank and a single blast-valve mechanism.

It is a further object of the present invention to improve upon themulti-break interrupting structure of the aforesaid application,rendering it more suitable for synthetic tests for testing a single unitby employing a separate reservoir chamber associated with each of aplurality of arc-extinguishing units.

In addition, it is a feature of the present invention to utilize thehigh-pressure reservoir chamber of the aforesaid interrupting structureas a supply chamber, which is only communicated with the severalreservoir chambers in the breaker-closed position. During thebreaker-opening operation, the supply valve associated with thehighpressure reservoir chamber is closed, and a separate valve structureassociated with each of the gas-blast interrupting units is opened topermit a measured quantity of compressed gas' to flow into therespective gas-blast interrupting unit.

Still a further object of the present invention is to provide animproved compressed-gas circuit interrupter, particularly adaptable forhigh-power service, in which the several blast valve'structures areinterrelated in a positive manner and are immediately opened at thebeginning of a circuit-breaker opening operation.

A further object of the present invention is to provide an improvedcompressed-gas circuit interrupter in which a measured quantity ofcompressed gas is forced into each of a plurality of serially-relatedcompressed-gas interrupting units so that substantially identicalinterrupting conditions exist at each of said gas-blast interruptingunits.

Another object of the present invention is to provide an improvedcompressed-gas circuit interrupter in which a novel operating linkageinterconnects the movable contact structure and the movable valvestructure of a circuit interrupter of the foregoing type.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings, inwhich:

FIGURE 1 is a perspective view of a three-phase highpower compressed-gascircuit interrupter embodying the principles of the present invention;

FIG. 2 is an enlarged side elevational view, partially in verticalsection, of the bridging arc-extinguishing assemblage disposed withineach of the three tank structures illustrated in FIG. 1, and operable tointerrupt one of the phase circuits of the three-phase circuitinterrupter of FIG. 1, the contact structure being illustrated in theclosed-circuit position;

FIG. 3 is a considerably enlarged fragmentary vertical sectional viewtaken through the interrupting unit and valve structure disposedimmediately adjacent the highpressure reservoir chamber, again thecontact structure being illustrated in the closed-circuit position; and,

FIG. 4 is an enlarged fragmentary view taken through the interruptingunit and valve structure at the extreme left-hand end of the bridginginterrupting assemblage, as shown in FIG. 2, again the contact structureand blastvalve structure being illustrated in the closed-circuitposition.

Referring to the drawings, and more particularly to FIG. 1 thereof, thereference numeral 1 generally designates a three-phase three-polehigh-power compressedgas circuit interrupter adaptable for controllingthe three phases of a transmission system.

As shown in FIG. 1, generally the circuit interrupter 1 includes aplurality of spaced grounded tank structures 2 mounted upon supports 3to a pair of longitudinally extending steel beams 4. In addition, thetank structures 2 are mechanically interconnected by an enclosed tube 5surrounding a longitudinally-operable operating rod, not shown. As aresult, the entire circuit-interrupting assemblage 1 may be bodilylifted by a crane and readily transported to its site in the field foroperation.

Disposed adjacent the end tank structure 2, as illustrated in FIG. 1, isa mechanism housing compartment 6, which houses a suitable operatingmechanism, which may be of any conventional type, such as pneumatic,solenoid-actuated, or hydraulic mechanism. The operating mechanism, notshown, disposed within the mechanism compartment 6 is operable, attimes, to effect longitudinal reciprocal movement of the interconnectingoperating rod, not shown, disposed within the interconnecting tubularhousing 5. It will be noted that terminal bushings 7, 8 extenddownwardly interiorly through supporting sleeves 9 and into the generalinterior of each tank structure 2. As shown in FIG. 2, the interior ends10 of the terminal bushings 7, 8 serve to fixedly support into anoperative position a bridging arc-extinguishing assemblage, generallydesignated by the reference numeral 13.

As set forth in the aforesaid Yeckley et a]. patent application SerialNo. 788,668, the operating mechanism for the circuit interrupter 1 isarranged to effect simultaneous movement of the several movable contactassemblages 14 associated with the arc-extinguishing assemblages 13enclosed within the respective tank structures 2.

With further reference to FIG. 2, it will be noted that eacharc-extinguishing assemblage 13 generally comprises a pair of spaced endsupport castings 15, 16, between which are supported and bolted a pairof spaced longitudinally-extending support bars 18. The support bars 18fixedly support into position a plurality of seriallyrelated gas-blastorifice-type interrupting units, generally designated by the referencenumeral 20.

Each gas-blast orifice-type interrupting unit 20 generally comprises arelatively stationary contact structure, designated by the referencenumeral 21, and including a plurality of circumferentially-disposedcontact fingers 22 and a substantially centrally located arcing horn 23.Cooperable with the relatively stationary contact structure 21 is atubular movable contact structure 24.

The several movable contact structures 24 are fixedly secured adjacentthe central portions of a plurality of crossbars which mechanicallyinterconnect a pair of spaced longitudinally-extending operating rods26. Disposed at the left-hand end of the movable contact assemblage 14,as viewed in FIG. 2, is a movable spring seat 27, against which isseated a heavy accelerating compression spring 28. The right-hand end ofthe accelerating spring 28, as viewed in FIG. 2, seats against astationary seat portion, not shown, associated with the support casting15. As a result, the accelerating compression spring 28 is effective tobias the movable contact assemblage 14 in a leftward opening direction,as viewed in FIG. 2, effecting thereby separation between the severalmovable contacts 24 from the relatively stationary contact structures21, thereby establishing a plurality of serially-related arcs, notshown.

To assist in effecting the extinction of the are drawn at each of theseveral compressed-gas orifice-type interrupting units 20, there isprovided an insulating orifice structure 29 providing an orifice opening30, through which the established arc is drawn. Gas-blast means 31,hereinafter more particularly described, is effective to cause ablasting of compressed gas through each of the orifice structures 29 andthrough the orifice openings 30 thereof to effect rapid extinction ofthe several seriallyrelated arcs.

It is a novel and important feature of the present invention thatassociated with each of the plurality of compressed-gas interruptingunits 20 is a separate storage volume or gas-reservoir chamber 32 forcontaining a predetermined quantity of high-pressure gas. This gas issupplied during the closed position of the interrupter 1 by a supplyvolume or chamber 11 disposed at the righthand end of thearc-extinguishing assemblage 13, as viewed in FIG. 2, and connected by afeed conduit 33 to an externally-located auxiliary high-pressurereservoir chamber, not shown.

With reference to FIG. 3 of the drawings, it will be noted that there isprovided a longitudinally extending insulating valve rod, designated bythe reference numeral 34, and having operatively associated therewith aplurality of sleeve valves 35. Preferably, each sleeve valve 35 has anannular recess portion 36, within which is positioned an O-ring 37. Inaddition, the right-hand end 38 of each sleeve valve 35 makes abuttingengagement with a resilient annular valve seat 39, the requisite springpressure being provided by a biasing spring 40. The valve rod 34 isbiased toward the left by a spring 17, shown in FIG. 2.

As shown in FIG. 3, the right-hand end of the valve rod 34 hasassociated therewith a supply valve 41, which seats against a valve seat42, and serves to interrupt communication between the interior 43 of thehigh-pressure storage chamber 11 and the several gas reservoir chambers32 associated with the plurality of interrupting units 20.

A compression spring 44 is associated with the supply valve 41 andserves to efiect closing of the same against the valve seat 42 when theactuating valve rod 34 is in its leftward opening position, not shown.As a result, in

the closed-circuit position of the interrupter, as illustrated in FIGS.2 and 3 of the drawings, there is provided'in tercommunication betweenthe interior 43 of the highpressure storage chamber 11 and the severalgas reservoir chambers 32. This is provided by the opened valve 41 andthe gas passages 46 provided through each of the tubular sleeve-valvestructures 35.

To interrelate opening movement of the movable contact structure 14 withopening of the several sleeve valves 35 and simultaneous closing of thesupply valve 41, there is provided an operating linkage, generallydesignated by the reference numeral 47, and including a rotatablecrankarm assembly 48 journaled on a stationary pivot 49 and having aplurality of crank-arms 50, 51. The crank-arm 50 is pivotally connected,as at 52, to an insulating operating rod 53, in turn pivotallyconnected, as at 54, to an internally-disposed crank-arm 55.

The crank-arm 51 is pivotally connected, as at 56, to a floating link57, the upper end of which, as viewed in FIG. 2, is pivotally connected,as at 58, to a crank arm 59. The crank arm 59 is clamped, by a clampingportion 59a, to a crank shaft 60.

As illustrated more clearly in FIG. 3 of the drawings, the crank shaft60 has a crank portion 61 pivotally connected, as at 62, to a drive link63. The driving link 63 is pivotally connected, as at 64, to acrank-shaft assembly 65. The crank-shaft assembly 65 has a pair of crankarms 66, 67. The crank-arm 66, as shown, is pivotally connected to thepivot pin 64. The crank-arm 67, on the other hand, has a pin 69, whichmoves within an elongated slot 70 associated with a link 71 pivotallyconnected, as at 72, to the right-hand extremity of the valve-actuatingrod 34.

It will be noted, consequently, that the provision of the elongated slot70 within the link 71 and the drive pin 69 collectively constitute alost-motion connection, generally designated by the reference numeral74, interconnecting the valve-operating rod 34 and the crank-armassembly 65 In the closed-circuit position of the circuit interrupter 1,as viewed in FIGS. 2 and 3 of the drawings, it will be apparent that theelectrical circuit passing through the interrupter comprises theterminal bushings 7, 8, conducting support brackets 15, 16, and theseveral interrupting units 20, comprising the arc-extinguishingassemblage 13. The electrical circuit extends in an obvious mannerbetween the several movable contacts 24 and the relatively stationarycontacts 21. As illustrated more in detail in the aforesaid patentapplication Serial No. 788,668, the right-hand end of each relativelystationary contact structure 21 has associated therewith a relativelystationary sliding finger construction 76, which makes slidingcontacting engagement with the adjacent movable contact rod 24.

During the closed-circuit position of the interrupter, as shown in FIGS.2 and 3, the high-pressure supply chamber 11 communicates through theopen supply valve 41 with the several reservoir chambers 32, so thatrelatively high pressure gas exists in all of the reservoir chambers 32.

To effect an opening operation of the circuit interrupter 1, suitablemechanism, not shown, disposed within the mechanism compartment 6(FIG. 1) is unlatched, and an accelerating spring 78 disposed within theend of the interconnecting tube 5, together with the severalaccelerating springs 28, cooperate collectively to effect leftwardopening movement of the movable contact assemblages 14 associated witheach of the three arc-extinguishing assemblages 13 of the several tankstructures 2.

There will immediately occur counter-clockwise opening rotation of thecrank-arm assembly 48. This will permit through the linkage, previouslydescribed, immediate leftward opening movement of the valve rod 34 whichis biased by the spring 17. In addition, an interconnecting link 80,pivotally interconnecting the crankarm 81 of the crank-shaft assembly 60and the laddershaped movable contact assemblage 14 permits openingSeparating movement of the several movable contacts 24 and stationarycontact structures 21. The separation between the several movablecontacts 24 and the relatively stationary contact structures 21 draws aplurality of serially-related arcs, not shown, through the orificeopenin-gs 30 of the insulating orifice structures 29.

Simultaneously with the foregoing action, there occurs opening of theseveral sleeve valves 35 permitting the blasting of gas from eachreservoir chamber 32 into the respective gas-blast interrupting unit 20.As a result, each gas-blast interrupting unit 20 is supplied with apredetermined quantity of compressed gas at the desired highpressurelevel to quickly effect extinction of the are drawn within therespective orifice structure 29. The several arcs are quicklyextinguished, and the movable contacts 24 continue toward the left to anisolating position, not shown. In the fully open-circuit position of thecontact structure 14, it will be noted that the several sleeve valves 35are open, as forced open by the shoulder portions 82 (FIG. 3) of thevalve-rod assembly 35, and at this'time the supply valve 41 is closed.As a result, pressure equalization occurs between the reservoir chambers32 and the general interior 84 within the tank structure 2.

During the closing operation, the mechanism disposed within themechanism compartment 6 (FIG. 1) is effective to effect longitudinalmovement of the operating rod, not shown, disposed within theinterconnecting tubular housing and effect counter-clockwise rotation ofthe several crank-arms 55 associated with each of the tank structures 2.This will, in turn, eifect leftward closing movement of the insulatingoperating rod 53 and consequent clockwise rotation of the crank-armassembly 47. Through the linkage, this will effect rightward closingmovement of the movable contact assemblage 14 and closing of the severalsleeve valves 35, with consequent opening action occurring at the supplyvalve 41. I

The opening of the supply valve 41, will permit highpressure gasdisposed within the interior 43 of the highpressure supply chamber 11 topass longitudinally through the passages 46, associated with the sleevevalves 35, and enter the several storage volumes 32 in readiness for thenext opening operation of the circuit interrupter 1.

The dead-tank circuit-interrupting structure, set forth in the aforesaidYeckley et al. patent application, utilizes a multi-break type ofinterrupting structure, which has a single blast valve located at oneend of the structure. Operation of the contacts actuates the blast valveand provides a flow to each of the breaks through insulating tubes ofvarying lengths. This arrangement, because of the interdependence offlow to each of the breaks, is diificult to verify in the laboratory. Ifa single break is tested with the other two breaks electrically shortedout, then the flow through the two shorted breaks acts as somewhat of aby-pass on the flow to the break being tested and, therefore, results ina diminution of flow to the tested break. In order to obtain maximumfault current on such tests, it is necessary to test a single break.There is, consequently, the difliculty of verifying the interruptingstructure set forth in the aforesaid Yeckley et al. patent application.

The present invention concerns a compressed-gas circuit-interruptingstructure which is in many respects similar to that described in theaforesaid Yeckley et al. patent application, but which has theadditional feature of storage means for the gas provided at each of thebreaks, so that the flow of gas to each break is independent of eachother. The high-pressure gas behind each break is stored in theinsulating reservoir chamber 32. The slide valves 35 are mounted on aninsulating operating valve rod 34, which is connected through a leversystem to the contact operating lever and consequently operating rod.The spring assembly 17 at the other end of the valve rod 34 providesacceleration of the valve rod 34 to the open position when the breaker 1is open. The supply volume 11 provides additional storage of gas behindthe storage volumes 32 in the breaker closed position. As a consequence,when the circuit interrupter 1 opens, the valve 41, mounted on the valverod 34, immediately closes off the passage 12 between the reservoirs 11,32. The purpose of the supply volume 11, therefore, is to provide quickfilling of reservoirs 32 when the breaker 1 is reclosed. The supplyvolume 11 is connected to an external reservoir through the insulatingtube 33.

It will be observed that the lever system 47, as shown, provides forimmediate operation of the valve actuating rod 34 upon opening of thebreaker 1. The lost-motion connection 74 allows the movable contacts 24of the circuit interrupter 1 to continue to open after the valves 35have completed their stroke.

From the foregoing description, it will be apparent that there isprovided an improved multi-break double-pressure type of circuitinterrupter for use in dead-tank structures of the type set forth in theaforesaid Yeckley et al. patent application. The structure has manyimportant advantages:

(1) An interrupting structure which lends itself very nicely to unittesting of single breaks because of the independence of the gas flow toeach break.

(2) The interrupting structure provides a metered flow of gas to eachbreak.

(3) The disclosed structure provides an interrupting structure in whichthe operation of the valves 35 admitting the high-pressure gas blast tothe contacts 21, 24 is directly coupled to the motion of the contacts24.

(4) It results in interrupting structure which is approximately the samein cost as that utilizing a single blast valve and employs a singleblast valve feeding gas to each break.

(S) The interrupting structure of the present invention lends itselfvery nicely to high-speed reclosing operation by virtue of the supplyvolume 11, which quickly feeds the unit reservoirs 32 at eachinterrupter unit 20.

From the foregoing description it will be apparent that there isprovided a novel type of compressed-gas circuit interrupter in which apredetermined quantity of highpressure gas is supplied at each of aplurality of compressed-gas arc-extinguishing units 20. The structure issuch that the high-pressure gas is supplied to each of the reservoirchambers 32 in the closed-circuit position of the interrupter 1 and byan independent flow of gas to each unit 20, highly efficient andeffective interrupting performanceis obtained at each interrupting unit20 during an opening operation of the circuit interrupter 1.

Although there has been illustrated and described a specificinterrupting structure, it is to be clearly understood that the same wasmerely for the purpose of illustratlon, and that changes andmodifications may readily be made therein by those skilled in the art,without departing from the spirit and scope of the invention.

We claim as our invention:

1. The combination in a multi-break compressed-gas circuit interrupterof a plurality of serially-related gasblast interrupting units, aseparate storage volume for each un t, a separate blast valve for eachunit, means defining a single supply volume, a supply valve foradmitting highpressure gas to said storage volumes, and means closingsaid single supply valve upon opening said first-mentioned blast valves.

2. A multi-break compressed-gas circuit interrupter includlng a groundedmetallic tank, a pair of spaced terminal bushings extending into saidtank and supporting an arc-extinguishing assemblage therein, saidassemblage ineluding a plurality of serially-related units, each unithaving a storage volume to supply the same with a blast of high-pressuregas, a high-pressure supply chamber to supply said storage volumes, anda single supply valve feedmg high-pressure gas to all the storagevolumes from the supply chamber in the breaker-closed position.

3. A multi-break compressed-gas circuit interrupter including meansdefining a high-pressure storage chamber, a single supply valvecontrolling the exhausting of gas out of said high-pressure storagechamber, a plurality of gas-blast interrupting units connected inseries, a gas reservoir chamber supplying gas to each gas-blastinterrupting unit, a blast valve connected with each gas reservoirchamber to control the blasting of gas out of the respective gasreservoir chamber toward the respective gas-blast interrupting unit toefiect arc extinction at said unit, a common control means effectingopening of the several blast valves and closing of the single supplyvalve, movable contact operating means, and means interconnecting saidcommon control means with said movable contact operating means.

4. A multi-break compressed-gas circuit interrupter including meansdefining a high-pressure storage chamber, a single supply valvecontrolling the exhausting of gas out of said high-pressure storagechamber, a plurality of gasblast interrupting units connected in series,a gas reservoir chamber feeding each gas-blast interrupting unit, ablast valve connected with each gas reservoir chamber to control theblasting of gas out of the respective gas reservoir chamber toward therespective gas-blast interrupting unit to effect are extinction at saidunit, a common control means eflecting opening of the several blastvalves and closing of the supply valve, movable contact operating means,means interconnecting said common control means with said movablecontact operating means, and means defining a lost-motion connectionbetween said common control means and said operating means so that theseveral movable contacts may continue to move to the open positionsubsequent to full opening travel of said common control means.

5. A multi-break compressed-gas circuit interrupter including meansdefining a high-pressure storage chamber, a single supply valvecontrolling the exhausting of gas out of said high-pressure storagechamber, a plurality of gasblast interrupting units connected in series,a gas reservoir chamber feeding each gas-blast interrupting unit, ablast valve connected with each gas reservoir chamber to control theblasting of gas out of the respective gas reservoir chamber toward therespective gas-blast interrupting unit to efiect arc extinction at saidunit, a common valve control rod interconnecting the plurality of blastvalves with said supply valve, whereby opening of the blast valves willcause simultaneous closing of the single supply valve, movable contactoperating means, and means interconnecting the valve control rod withsaid movable contact operating means.

6. A multi-break compressed-gas circuit interrupter in cluding meansdefining a high-pressure storage chamber, a single supply valvecontrolling the exhausting of gas out of said high-pressure storagechamber, a plurality of gasblast interrupting units connected in series,a gas reservoir chamber feeding each gas-blast interrupting unit, ablast valve connected with each gas reservoir chamber to control theblasting of gas out of the respective gas reservoir chamber toward therespective gas-blast interrupting unit to eliect arc extinction at saidunit, a common valve control rod interconnecting the plurality of blastvalves with said supply valve, whereby opening of the blast valves willcause simultaneous closing of the supply valve, movable contactoperating means, and means including a lost-motion connectioninterconnectig the valve control rod with said movable contact operatingmeans.

References Cited by the Examiner UNITED STATES PATENTS 2,491,112 12/49Jansson 200-148 FOREIGN PATENTS 1,222,392 1/ France. 1,247,592 10/60France.

BERNARD A. GILI-IEANY, Primary Examiner.

MAX L. LEVY, Examiner.

1. THE COMBNATION IN A MULTI-BREAK COMPRESSED GAS CIRCUIT INTERRUPTER OFA PLURALITY OF SERIALLY-RELATED GASBLAST INTERRUPTING UNITS, A SEPARATESTORAGE VOLUME FOR EACH UNIT, A SEPARATE BLAST VALVE FOR EACH UNIT,MEANS DEFINING A SINGLE SUPPLY VOLUME, A SUPPLY VALVE FOR ADMITTINGHIGHPRESSURE GAS TO SAID STORAGE VOLUMES, AND MEANS CLOSING SPAD SINGLESUPPLY VALVE OPENING SAID FIRST-MENTIONED BLAST VALVES.